An image stabilization process allows an image or video sequence to be captured, stored or rendered with a reduced (or eliminated) amount of apparent motion caused by a secondary, unintentional motion of an image or video sequence capture device with respect to a scene or object being captured, whilst preserving a dominant, intentional motion of the capture device. The image or video capture device could be a camera (digital or other), a camcorder (digital or other), or any other device capable of capturing an image or sequence of images for storage in the device or elsewhere.
It is desirable for images, or a sequence of images (hereinafter referred to as a “video sequence”), captured using an image capture device to be processed to provide image stabilization either during capture, using the image capture device, or when viewed or played back, using video playback equipment. The processing commonly takes the form of filtering or correction of the image or video sequence in order to remove undesirable elements such as motion blur, for example, which may be caused by movement of the image capture device during the capture procedure.
Several classes of image stabilization methods exist, for example mechanical, electromechanical, optical and electronic stabilization.
Recently, interest in the use of user-wearable image capture devices has resulted in stabilization methods being applied to images captured from these types of devices. Such user-wearable devices may have stabilization functionality built-in, or may rely on stabilization of captured image data being carried out in another system distinct from the device itself.
The nature of a user-wearable image capture device implies that any images captured from it will be intrinsically ‘noisy’ due to motion and vibrations introduced to the device by a user's movements, intentional or unintentional. Such ‘noisy’ image data may best be characterized as data which includes a secondary (to the data of the scene or object to be captured), undesirable element such as a low-frequency element in a video sequence due to a user walking or running, for example, or a high-frequency element in a video sequence due to a user travelling in a vehicle, for example. It will be appreciated that further types of undesirable data may be introduced into image data due to device rotation etc.
In order to reduce the problem of ‘noisy’ image data, the above-mentioned stabilization methods have been applied to captured sequences. For example, U.S. Pat. No. 5,502,484 describes a shake detection and correction method for use in video cameras and video signal reproducing apparatus. Further, U.S. Pat. No. 5,253,071 describes a method and apparatus for stabilizing an image produced in a video camera.
The above-mentioned stabilization techniques, when applied to sequences in which device motion can be dramatic, such as user wearable devices, for example, are not optimal, and a compromise is generally required between attenuating high frequency motion and obtaining a step response.